Disc (galaxy)
This article is about the flat disc component of a galaxy. For the type of galaxy with discs, see disc galaxy.
The Sculptor Galaxy (NGC 253) is an example of a disc galaxy
A disc is a component of disc galaxies, such as spiral galaxies, or lenticular galaxies.
The galactic disc is the plane in which the spirals, bars and discs of disc galaxies exist. Galactic discs tend to have more gas and dust and younger stars than galactic bulges or galactic haloes.
The galactic disc is mainly composed of gas, dust and stars. The gas and dust component of the galactic disc is called the gaseous disc. The star component of the galactic disc is called the stellar disc.
Inconsistent orbital velocities of stars
Main article: Galaxy rotation curve
It has been noted that the orbital velocity of stars in the disc of most disc galaxies is inconsistent with the amount of luminous matter calculated for the galaxy. A possible explanation for this problem is the non-luminous dark matter.
See also
- Galactic spheroid
- Galactic corona
- Tully–Fisher relation
- MOND (Modified Newtonian Dynamics)
Further reading
- Van Der Kruit, P. C.; Freeman, K. C. (2011). "Galaxy Disks". Annual Review of Astronomy and Astrophysics 49: 301. arXiv:1101.1771. Bibcode:2011ARA&A..49..301V. doi:10.1146/annurev-astro-083109-153241.
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